This invention relates generally to switches for railroad transportation systems, and particularly to switches for railroad transportation systems of the type which employ rotating drive shafts extending along railroad tracks upon which cars may be driven.
Recently, railroad transportation systems have been devised for transporting small cars or dollies in freight handling and distribution areas such as, for example, between loading docks and conveyor lines in manufacturing and processing plants. These systems may employ elongated circuitous rotatable drive shafts or tubes disposed between parallel rails as a means for propelling cars thereover. One such system is disclosed in U.S. Pat. No. 3,118,393. Here, a freely rotatable drive wheel is supported beneath a vehicle in resilient contact with the rotatable drive shaft. The drive wheel is oriented at an oblique angle with respect to the rotating drive shaft or tube whereby the drive shaft may produce a pushing force on the drive wheel which force has a component in the direction of the driving shaft and thus provides the driving force for the car. In this particular system the support means for the wheel permits the wheel to swivel and assume an orientation perpendicular to the axis of the drive shaft when the vehicle meets an obstacle and is stopped thereby. With the drive wheel positioned normally with respect to the direction of shaft extension the wheel imparts a breaking force to a moving car as the wheel skids over the rotating shafts. When the car has ceased its forward movement over the shaft, the drive wheel merely commences to rotate freely on the rotating shaft while the car remains stationary above the shaft.
In U.S. Pat. No. 3,356,040 a switch is disclosed for use with a transportation system of the type just described employing a rotating drive shaft. The disclosed switch connects two branch tracks which join together at approximately right angles in the shape of a T. A T-shaped assembly of rotating drive shafts is rotatably disposed between the rails. In order to effect a switching action a car traveling upon the tracks is brought to a stop at the T intersection and nudged laterally causing the drive wheel to more from one rotating tube to the other oriented normally thereto. The car or dolly is then driven off at 90.degree. relative direction with respect to its initial direction without swiveling of the car itself. Instead, the switching action is sensed by the car which initiates a swiveling action of the drive wheel to orient it in proper driving relation with respect to the new axis of the rotating drive shaft onto which it has been switched.
In systems of the type just described it is virtually necessary to completely arrest forward movement of cars at switching stations in order to effect a switching action. Once the car has come to a halt, it is also necessary to urge the car onto the new tracks on order to disengage the driving wheel from the drive shaft upon which it had been propelled into the switching station into engagement with the drive shaft propelling the car out from the switch. It is further necessary to sense the switching action and in response thereto to generate and transmit a signal for the driving wheel on the car to reorient itself obliquely with respect to the axis of the subsequent drive shaft and tracks. These actions, of course, require implementing equipment together with their costs for purchase and maintenance. The fact the cars must be brought to a complete stop at each switching station required further implementing equipment and detracts from transportation speed efficiency.
Accordingly, it is a general object of the present invention to provide an improved switch for a railroad transportation system employing a rotating drive shaft.
More specifically, it is an object of the present invention to provide a switch for a railroad transportation system employing a rotating drive shaft which switch does not necessitate a change in linear velocity of a car passing through the switch.
Yet another object of the invention is to provide a switch for a railroad transportation system employing a rotating drive shaft which switch is of simple and economical construction requiring a minimum of maintenance.
Yet another object of the invention is to provide an improved method of switching cars from one track to another in railroad transportation systems employing rotating drive shafts